With the recent increases in the level of integration density of semiconductor devices, it is becoming very important to deal with crystal defects of a semiconductor single crystal substrate (hereinafter referred to as a semiconductor substrate or also simply a substrate), from which a semiconductor device is formed, in particular, crystal defects formed in the vicinity of the surface of the single crystal substrate. If a semiconductor single crystal substrate on which any crystal defect is formed is used to produce a semiconductor device, the quality of the produced semiconductor device will be significantly affected. Therefore, in order to improve the quality of such a semiconductor device, it is necessary to evaluate crystal defects in the vicinity of the surface of a semiconductor single crystal substrate serving as the substrate of the semiconductor device, and to know the status thereof.
As an evaluation method for the semiconductor substrate, for example, a visual inspection has been conventionally performed in which the shape of distribution of crystal defects appearing on the surface of a semiconductor substrate is sketched under a light-condensing lamp to determine the length and the like of the crystal defects, then the measured results are accumulated, and the level of occurrence of the crystal defects is evaluated. As an evaluation method using a measurement device, an X-ray topography method or the like has been carried out in which X-rays are emitted to the substrate, and the X-ray diffraction intensity attributed to the crystal defects formed on the substrate is detected.
For example, in the case of using the above-described visual inspection to quantify the amount of slip dislocations formed on a semiconductor substrate, the slip dislocations observed visually are sketched, and the accumulated length of the slip dislocations will be further determined from the sketch. Therefore, significant time and labor is required. In addition, the test results vary because the measurement is based on human visual perception, and therefore the test needs to be performed by an experienced and skillful person.
In the case of using the above-described X-ray topography method to evaluate the crystal defects, defects that have occurred on the surface as well as the interior and the back surface will be observed. Therefore, it is difficult to evaluate the crystal defects present on the surface of the substrate and the crystal defects present in the interior or the like of the substrate while distinguishing between these defects.
Examples of the other methods using a measurement device include a method using a device that scans the surface of the semiconductor substrate with laser light, and measures the light scattering intensity from particles or the like. With this method, the device mechanically detects crystal defects, so that the variations in the test results can be reduced to a certain degree. However, crystal defects attributed to various crystal defects are contained in the detected crystal defects, and specific crystal defects such as a slip dislocation cannot be selectively quantified.
Patent Document 1 discloses a method in which the scattered light resulting from the laser light emitted to the surface of the semiconductor substrate is detected by a photodiode, and the crystal defects on the semiconductor substrate are evaluated. However, the method of Patent Document 1 is a destructive test that requires the labor of etching the semiconductor substrate in advance, and the accuracy of detection of crystal defects by the photodiode is insufficient.
On the other hand, Patent Documents 2 and 3 disclose methods in which the reflected light resulting from the laser light emitted to the surface of the semiconductor substrate is detected using a photoelectric element to evaluate the slip dislocation.